1. Field of the Invention
The present invention relates to an image sensing device and a camera module, and more particularly, to an image sensing device having a protection pattern on a microlens or microlenses, a camera module employing the image sensing device, and a method of forming the same.
2. Description of the Related Art
Camera modules capable of creating still images and moving pictures are widely used in mobile phones, digital cameras, video cameras, and closed circuit TVs. The camera module is composed of an image sensing device and a case. The image sensing device includes a solid-state image sensing device, such as a CMOS image sensor (CIS) or a charge coupled device (CCD). The solid-state image sensing device is a semiconductor device capable of changing an optical image signal from the outside into an electrical signal.
FIG. 1 is a cross-sectional view of a conventional CMOS image sensor, or CIS.
Referring to FIG. 1, an isolation layer 13 defining active regions 12 is provided in a semiconductor substrate 11. Photodiodes 17 are provided in the active regions 12. Each of the photodiodes 17 includes an n-type impurity region 16 and a p-type impurity region 15, which are sequentially stacked in the active region 12. The semiconductor substrate 11 having the photodiodes 17 is covered with a lower insulating layer 19.
Interconnections 21 and a bond pad 23 are disposed on the lower insulating layer 19. The interconnections 21 can be electrically connected to the photodiodes 17. The interconnections 21 are disposed so they do not hide the photodiodes 17. An upper insulating layer 25 covering the interconnections 21 is provided. The upper insulating layer 25 includes a pad window 25W exposing the bond pad 23. Color filters 27 are disposed in the upper insulating layer 25. A plurality of microlenses 29 are disposed on the upper insulating layer 25.
Light passing through the microlenses 29 is transformed into an electrical signal in the photodiode 17 via the color filters 27. The microlenses 29 function to maximize an amount of light reaching the photodiodes 17. That is, each of the microlenses 29 serves as a condenser lens.
However, each of the microlenses 29 has a generally hemispherical convex surface. Accordingly, a top surface of each of the microlenses 29 is not flat. As a result, contaminants such as particles P are easily adhered to the top surface of the microlenses 29. However, the adhered particles P are very difficult to remove due to the uneven structure. Furthermore, the microlenses 29 are exposed to physical damage, such as scratches.
The particles P and the physical damage block and alter the light passing through the microlenses 29.
Meanwhile, the formation of the pad window 25W includes processes of forming a photoresist pattern (not illustrated) covering the microlenses 29, etching the upper insulating layer 25 until the bond pad 23 is exposed, and removing the photoresist pattern. The removal of the photoresist pattern can be performed by known ashing and cleaning processes.
Here, the non-flat or bumpy top surface of the microlenses 29 makes complete removal of the photoresist pattern difficult. That is, the removal of the photoresist pattern requires a complicated cleaning process, which leads to deterioration of production efficiency.
Also, another image sensor having a microlens and a method of forming the same are disclosed in Japanese Patent. Publication No. 2001-308300 entitled “Solid-State Image Element and Its Manufacturing Method” by Hiroki.
According to Hiroki, a solid-state image sensing device having several microlenses and a method of forming the same are provided. The microlenses are arranged at short intervals, but not immediately adjacent to one another as in FIG. 1. In such a case, complicated techniques for preventing physical damage of the microlenses and surface adhesion of contaminants are required in Hiroki.